Effects of a selective 5-HT1B receptor agonist and antagonists in animal models of anxiety and depression.

The purpose of the present study was to investigate the effects of the selective 5-HT1B receptor agonist CP 94253, the selective 5-HT1B receptor antagonist SB 216641, and the 5-HT1B/1D receptor antagonist GR 127935 in behavioral tests commonly used to predict anxiolytic- and antidepressant-like activity. Diazepam and imipramine were used as reference drugs. In the Vogel conflict drinking test, CP 94253 (1.25-5 mg/kg), SB 216641 (2.5-5 mg/kg) and GR 127935 (5-10 mg/kg) showed anxiolytic-like effects comparable to that of diazepam (2.5-5 mg/kg). In the elevated plus-maze test, antianxiety-like activity of all the compounds tested was also observed: the effects of CP 94253 (2.5 mg/kg) and SB 216641 (5 mg/kg) were similar to that of diazepam (5 mg/kg), while GR 127935 (up to 40 mg/kg) was less active. In the four-plate test, the compounds tested (5-10 mg/kg) produced anxiolytic-like effects which were weaker than that of diazepam (2.5-5 mg/kg). In the forced swimming test, CP 94253 (5-10 mg/kg), like imipramine (30 mg/kg), showed anti-immobility action, whereas SB 216641 (2.5-10 mg/kg) and GR 127935 (20-40 mg/kg) did not affect the immobility time in mice. The results indicate that the selective agonist (CP 94253) and antagonists (SB 216641 and GR 127935) of 5-HT1B receptors produce effects that are characteristic of anxiolytics, in the preclinical models used; however, CP 94253 also behaves like an antidepressant drug.

The anxiolytic-like activity of AIDA (1-aminoindan-1,5-dicarboxylic acid), an mGLu 1 receptor antagonist.

In the present study we examined the effects of 1-aminoindan-1,5-dicarboxylic acid (AIDA), regarded as a selective and competitive mGluR1 antagonist, in animal models of anxiety. Diazepam (1-10 mg/kg) was used as a reference drug. After intraperitoneal administration, AIDA (0.5-2 mg/kg) produced anxiolytic-like effects in the conflict drinking test and the elevated plus-maze test in rats; however, in doses up to 8 mg/kg, it was inactive in the four-plate test in mice. AIDA tested at the effective doses in the conflict drinking test changed neither the treshold current nor water intake in rats compared to vehicle treatment. AIDA (in a dose of 4 mg/kg, but not lower) increased the exploratory locomotor activity of rats measured in the open-field test, but it did not disturb rat motor coordination in the rota-rod test. The above results indicate that selective mGluR1 antagonist AIDA induces antianxiety-like effects at a low risk of acute side effects characteristic of benzodiazepines. Further studies are required to identify the sites and the mechanism of action of AIDA.

Group III mGlu receptor agonists produce anxiolytic- and antidepressant-like effects after central administration in rats.

It was well established that compounds which decrease glutamatergic transmission via blockade of NMDA or group I mGlu receptors produce anxiolytic- and antidepressant-like action in animal tests and models. Since group III metabotropic glutamate receptor (mGluR) agonists are known to reduce glutamatergic neurotransmission by the inhibition of glutamate release, we decided to investigate potential anxiolytic- and/or antidepressant-like effects of group III mGluR agonists, after central administration in rats. It was found that group III mGluR agonists, (1S,3R,4S)-1-aminocyclo-pentane-1,3,4-tricarboxylic acid (ACPT-I) and 2-amino-4-(3-hydroxy-5-methylisoxazol-4-yl)butyric acid (HomoAMPA), given intrahippocampally, produced a dose-dependent anxiolytic-like effect in the conflict drinking test. The effects of ACPT-I and HomoAMPA were reversed by (RS)-alpha-cyclopropyl-4-phosphonophenyl glycine (CPPG), group III mGluR antagonist. Moreover, a dose-dependent antidepressant-like action of group III mGluR agonists, ACPT-I and (RS)-4-phosphonophenylglycine (RS-PPG), but not HomoAMPA, was found in behavioral despair test, after intracerebroventricular injections, and the effect of ACPT-I was reversed by CPPG. The results obtained indicate that group III mGluR agonists produce anxiolytic- as well as antidepressant-like effects in behavioral tests, after central administration in rats. The reduction of glutamate release by group III mGluR activation may be a possible mechanism underlying anxiolytic- and antidepressant-like properties of the tested compounds. In conclusion, the results of our studies indicate that group III mGlu receptor agonists may play a role in the therapy of both anxiety and depression.

Multiple MPEP administrations evoke anxiolytic- and antidepressant-like effects in rats.

Several lines of evidence suggest a crucial involvement of glutamate in the mechanism of action of anxiolytic and antidepressant drugs. The involvement of group I mGlu receptors in anxiety and depression has also been proposed. In view of the recent discovery of anxiolytic- or antidepressant-like effects of acute injections of 2-methyl-6-(phenylethynyl)-pyridine (MPEP), a selective and brain penetrable mGlu5 receptor antagonist, we designed the present study to examine anxiolytic- and/or antidepressant-like effects of multiple administrations of this drug. The anxiolytic-like effects of MPEP were evaluated in rats using the conflict drinking test. The antidepressant-like effect was estimated using the rat olfactory bulbectomy model of depression. Seven subsequent injections of MPEP (1 mg/kg) significantly (by 320%) increased the number of shocks accepted during the experimental session in the Vogel test. MPEP given once daily at a dose of 10 mg/kg, restored the learning deficit of bulbectomized rats after 14 days of treatment, remaining without any effect in the sham-operated animals. N-methyl-D-aspartic acid (NMDA)-induced convulsions in mice were not affected by a single injection of MPEP (30 mg/kg) indicating that at this dose MPEP did not block NMDA receptors. The results indicate that the prolonged blockade of mGlu5 receptors exerts anxiolytic- and antidepressant-like effects in rats. No tolerance to anxiolytic-like action occurs. The previously mentioned results further indicate that antagonists of group I mGlu receptors may play a role in the therapy of both anxiety and depression.

The antianxiety-like effects of antagonists of group I and agonists of group II and III metabotropic glutamate receptors after intrahippocampal administration.

RATIONALE: Substances acting as agonists of group II mGlu receptors with joint group I mGlu receptor antagonist effects, or group II mGlu receptors agonists, were shown to induce antianxiety-like effect in rats after intrahippocampal administration. OBJECTIVE: The present study was undertaken to establish whether a more selective group I, II, III mGlu receptors agonists/antagonists induce anxiolytic-like effects after injection to the hippocampus. METHODS: (S)-4-Carboxyphenylglycine [(S)-4CPG] and 7-(hydroxyimino)cyclopropan[b]chromen-1alpha-carboxylic ethyl ester (CPCCOEt), selective antagonists at group I mGlu receptors, or (+)1S, 2S, 5R, 6S-2-aminobicyclo[3.1.0]hexane-2,6-dicarboxylic acid (LY354740) and (2S, 1'S, 2'S)-2-(carboxycyclopropyl)glycine (L-CCG-I), two selective agonists of group II mGlu receptors, as well as (1S, 2S, 4S, 5S)-2-aminobicyclo[2.1.1]hexane-2,5-dicarboxylic acid-I (ABHxD-I), an agonist at all three groups of mGlu receptors and L-serine-O-phosphate (L-SOP), an agonist at group III mGlu receptors, were used. All compounds were administered into the CA1 region of the dorsal hippocampus. The conflict drinking Vogel test in rats was used to estimate the anxiolytic-like effects of all the compounds. RESULTS: After intrahippocampal administration, both selective group I mGlu receptors antagonists (S)-4CPG and CPCCOEt, as well as the selective agonists of group II mGlu receptors LY 354740 and L-CCG-I, and an agonist of group III mGlu receptors, L-SOP, induced anticonflict effects. CONCLUSION: Selective antagonists of group I mGlu receptors and agonists of group II and group III mGlu receptors exhibit anxiolytic-like activity in the conflict drinking test. It seems that the hippocampus may be one of the brain structures involved in the anticonflict effect of mGlu receptor agonists/antagonists.

Potential anxiolytic- and antidepressant-like effects of MPEP, a potent, selective and systemically active mGlu5 receptor antagonist.

1. Several lines of evidence suggest a crucial involvement of glutamate in the mechanism of action of anxiolytic and/or antidepressant drugs. The involvement of group I mGlu receptors in anxiety and depression has also been proposed. Given the recent discovery of a selective and brain penetrable mGlu5 receptor antagonists, the effect of 2-methyl-6-(phenylethynyl)-pyridine (MPEP), i.e. the most potent compound described, was evaluated in established models of anxiety and depression. 2. Experiments were performed on male Wistar rats or male Albino Swiss or C57BL/6J mice. The anxiolytic-like effects of MPEP was tested in the conflict drinking test and the elevated plus-maze test in rats as well as in the four-plate test in mice. The antidepressant-like effect was estimated using the tail suspension test in mice and the behavioural despair test in rats. 3. MPEP (1 - 30 mg kg(-1)) induced anxiolytic-like effects in the conflict drinking test and the elevated plus-maze test in rats as well as in the four-plate test in mice. MPEP had no effect on locomotor activity or motor coordination. MPEP (1 - 20 mg kg(-1)) did shorten the immobility time in a tail suspension test in mice, however it was inactive in the behavioural despair test in rats. 4. These data suggest that selective mGlu5 receptor antagonists may play a role in the therapy of anxiety and/or depression, further studies are required to identify the sites and the mechanism of action of MPEP.

2-H- and 2-acyl-9- [omega-[4-(2-methoxyphenyl)piperazinyl]-alkyl]-1,2,3,4-tetrahydro-beta-carbolines as ligands of 5-HT1A and 5-HT2A receptors.

Three series of new unsubstituted or 2-acyl 1,2,3,4-tetrahydro-beta-carbolines (THBC), connected to 1-(o-methoxyphenyl)piperazine by 2-, 3- or 4-membered alkylene spacer (3, 4 or 5, respectively) in position 9, were synthesized and their 5-HT1A/5-HT2A receptor affinities and functional in vivo activities were investigated. Radioligand binding studies showed that unsubstituted (a) and acyl (b-f) derivatives with prop-1,3-ylene (4) and particularly with but-1,4-ylene (5) spacer had a high 5-HT1A receptor affinity (Ki = 30-110 nM), whereas the 5-HT1A affinity of derivatives with ethylene spacer (3) was low. All those compounds (except 5c, Ki = 44 nM) did not distinctly bind to 5-HT2A receptors. The obtained results indicated that the length of an alkylene chain was a crucial parameter for determining 5-HT1A receptor affinities of the tested compounds, while acyl substituents in position 2 of THBC were not important for their 5-HTIA/5-HT2A activities. It was also demonstrated that the few selected compounds (4d, 5a-c and 5e) with the highest affinity (Ki up to 50 nM) for 5-HT1A receptors, administered at doses of 10-20 mg/kg, behaved like antagonists of postsynaptic 5-HT1A receptors, as they reduced the 8-OH-DPAT (5-HT1A agonist)-induced lower lip retraction and behavioral syndrome in rats. Moreover, 4d seemed to be an agonist of presynaptic 5-HT1A receptors, since the hypothermia induced by its administration was attenuated by WAY 100635 (5-HT1A antagonist). Compound 5c, 5-HT2A receptor ligand, demonstrated an antagonistic activity, as it inhibited the (+/-)DOI (5-HT2A agonist)-induced head twitches in mice. The obtained results of in vivo studies suggest that introduction of different acyl substituents in position 2 of THBC with propylene or butylene spacer between tricyclous and arylpiperazine moiety is insignificant for the postsynaptic 5-HTIA receptor activity of the compounds tested in vivo. On the other hand, only compound 5c with an acryloyl group and a butylene chain behaved like a 5-HT1A/5-HT2A antagonist.

Stimulation of group II metabotropic glutamate receptors or inhibition of group I ones exerts anxiolytic-like effects in rats.

Using the conflict drinking Vogel test in rats as a model we examined the anxiolytic-like activity of (S)-4-carboxyphenylglycine (S-4CPG), an antagonist of group I metabotropic glutamate receptors (mGlu receptors), of (RS)-a-methylserine-O-phosphate-monophenyl ester (MSOPPE), an antagonist of group II mGlu receptors, and of (2S,1'S,2'S)-2-(carboxycyclopropyl)glycine (L-CCG-I), an agonist of group II mGlu receptors. The obtained results indicate that intrahippocampal administration of S-4CPG and L-CCG-I, but not MSOPPE to rats produces a dose-dependent anticonflict effect, which is unrelated to the reduced perception of the stimulus or to an increased thirst drive. The hippocampus may be one of the neuroanatomical sites of the anxiolytic-like effects of either agent.

Influence of the aliphatic spacer length on the 5-HT1A receptor activity of new arylpiperazines with an indazole system.

Novel arylpiperazines (1a, 1c, 2a and 2c), containing a terminal 1- or 2-indazolyl fragment and a di- or tetramethylene aliphatic spacer, were synthesized and their 5-HT1A and 5-HT2A receptor affinities were determined. All those compounds showed a potent affinity for 5-HT1A receptors (Ki = 5-16 nM) and were evaluated for an intrinsic activity at those receptors. In order to determine a 5-HT1A agonistic effect of the investigated compounds, their ability to induce a lower lip retraction in rats and a behavioral syndrome (flat body posture and forepaw treading) in reserpinized rats were tested, whereas their 5-HT1A antagonistic activity was assessed via inhibition of those symptoms produced by 8-hydroxy-2-(di-n-propylamino)tetralin hydrobromide (8-OH-DPAT). The effect of spacer length on the 5-HT1A activity of the tested compounds was discussed in comparison with that of the three-methylene analogs (1b and 2b) described earlier. Both dimethylene derivatives (la and 2a) were characterized as weak postsynaptic 5-HT1A receptor antagonists. Compounds 1c (1-indazolyl analog) and 2c (2-indazolyl analog) with a tetramethylene aliphatic chain were classified as a postsynaptic 5-HT1A antagonist and a partial 5-HT1A agonist, respectively. Furthermore, the latter showed a moderate anxiolytic-like effect (conflict drinking Vogel's test in rats) and a weak antidepressant-like activity (forced swimming Porsolt's test in rats).

The influence of the benzodiazepine receptor antagonist flumazenil on the anxiolytic-like effects of CGP 37849 and ACPC in rats.

In this paper we examined the effect of flumazenil (Ro 15-1788, 10 mg/kg), a benzodiazepine receptor antagonist, on the anticonflict activity of DL-(E)-2-amino-4-methyl-5-phosphono-3-pentenoic acid (CGP 37849), a competitive N-methyl-D-aspartate (NMDA) receptor antagonist, and 1-aminocyclopropanecarboxylic acid (ACPC), a partial agonist at glycine(B) receptors, in the Vogel conflict drinking test in rats. The effect of flumazenil on the anxiolytic-like (in the plus-maze test) and the anticonvulsant (in the maximal electroshock-induced seizures) activities of CGP 37849 in rats was also studied. Diazepam was used as a reference drug. CGP 37849 (2. 5-5 mg/kg), ACPC (50-200 mg/kg) and diazepam (2.5-5 mg/kg) significantly and dose-dependently increased the number of shocks accepted during experimental sessions in the conflict drinking test. Flumazenil partly but significantly reduced the anticonflict effect of CGP 37849, and it fully blocked the anticonflict effect of ACPC and diazepam. CGP 37849 (2.5-5 mg/kg) and diazepam (2.5-5 mg/kg) were also active in the plus-maze test, as they significantly increased the percentage of the time spent in and entries into the open arms of the plus-maze, both those effects having been antagonized by flumazenil. Flumazenil alone was inactive in both the conflict drinking and the plus-maze tests. In the maximal electroshock-induced seizures, both CGP 37849 (2.5-5 mg/kg) and diazepam (5-10 mg/kg) produced anticonvulsant effects, of which only that of diazepam was antagonized by flumazenil. The results of the present study showing antagonism of flumazenil towards the anxiolytic-like effects of CGP 37849 and ACPC suggest involvement of benzodiazepine receptors in such an activity of the NMDA and glycine(B) receptor ligands, respectively, which may be due to a possible interaction between NMDA and GABA/benzodiazepine systems. The lack of effect of the benzodiazepine antagonist on the anticonvulsant activity of CGP 37849 indicates that involvement of benzodiazepine receptors in the pharmacological action of the NMDA antagonist is not a general phenomenon.

Anxiolytic-like effects of group I metabotropic glutamate antagonist 2-methyl-6-(phenylethynyl)-pyridine (MPEP) in rats.

We examined the anxiolytic-like activity of2-methyl-6-(phenylethynyl)-pyridine (MPEP) using the conflict drinking Vogel test in rats as a model. MPEP is a selective and brain-penetrable mGlu5 receptor antagonist, the most potent compound described so far. The results indicate that MPEP produced a dose-dependent anticonflict effect in rats. These data suggest that selective mGlu5 receptor antagonists may become a new class of anxiolytics.

Structure-activity relationship studies of CNS agents. Part 38. Novel 1,4-benzoxazin-3(4H)-one, 1,2-benzoxazolin-3-one and 1,3-benzoxazolin-2,4-dione arylpiperazine derivatives with different 5-HT1A and antagonistic 5-HT2A activities.

New 1-arylpiperazine (series d-f) and 1,2,3,4-tetrahydroisoquinoline (series g) derivatives of 1,4-benzoxazin-3(4H)-one 1, 1,2-benzoxazolin-3-one 2, and 1,3-benzoxazolin-2,4-dione 3 with an n-butyl chain were synthesized in order to explore the effect of spacer elongation on their binding affinity and in vivo functional activity at 5-HT1A and 5-HT2A receptors in comparison with trimethylene analogues (a, bc). 5-HT1A receptor binding constants of derivatives 1d-g, 2d-f, and 3d-f were very high (Ki = 1.25-54 nM), and 5-HT2A affinities were maintained at a similar, high level (Ki = 27-85 nM) for series d and e, and moderate (Ki = 246-495 nM) for series f. In respect of a spacer, the obtained results showed either no effect or a slight increase in the 5-HT1A/5-HT2A affinity in case of derivatives of 1 and 2, respectively. A striking effect was observed for derivatives 3d and 3f, whose 5-HT1A affinity was reinforced by two orders of magnitude with a simultaneous decrease in 5-HT2A binding constants in comparison with trimethylene analogues. As shown by X-ray crystallography, this phenomenon may be attributed to the position of non-carbonyl oxygen atom in the amide moiety. In vivo studies demonstrated that compounds 1e-g, 2d-f, and 3f behaved like typical postsynaptic 5-HT1A receptor antagonists, whereas 3d and 3e might be qualified as their potential partial agonists. Moreover, 1e, 2e, and 3e demonstrated 5-HT2A receptor antagonistic properties. Of the tested compounds, two derivatives showed some very outstanding properties: 3e may be regarded as a potential anxiolytic and/or antidepressant agent, while 3f as a new potent 5-HT1A antagonist.

Tolerance to anxiolytic- and antidepressant-like effects of a partial agonist of glycineB receptors.

The present study examined effects of acute and repeated administration of 1-aminocyclopropanecarboxylic acid (ACPC), a partial agonist of glycineB receptors, in the conflict drinking test and the forced swim test in rats. Diazepam and imipramine were used, respectively, as reference drugs in those tests. In the conflict drinking test, acute administration of ACPC (200 mg/kg) increased fivefold the number of punished licks. A three- and fivefold increase in the number of punished licks was observed in rats treated repeatedly with ACPC (200 mg/kg daily; 14 days) and challenged with the same dose of the drug 24 h or 4 days later, respectively. A single injection of ACPC (400 mg/kg) reduced by 40% the immobility time in the forced swim test. In rats treated repeatedly with ACPC (400 mg/kg daily; 14 days) and challenged with the same dose 24 h or 4 days later, the drug either produced no significant effect or reduced the immobility time by 50%, respectively. On the other hand, no changes in anxiolytic- and antidepressant-like effects of chronically administered diazepam (10 mg/kg daily; 14 days) and imipramine (30 mg/kg daily; 14 days), respectively, were observed. The above results indicate that tolerance develops to the anxiolytic- and, particularly, to the antidepressant-like activity of ACPC.

1,2,3,4-tetrahydroisoquinoline derivatives: a new class of 5-HT1A receptor ligands.

Three series of new N-substituted 1,2,3,4-tetrahydroisoquinolines with 2-, 3-, and 4-membered alkyl chains (a, b, and c, respectively) were synthesized, and the effect of some structural modifications on their 5-HT1A receptor affinities and functional properties was discussed. It was found that the volume of the terminal amide substituent was a crucial parameter which determined 5-HT1A receptor affinities of the tested compounds, while the in vivo activity seemed to depend on both the R-volume and the length of a hydrocarbon chain. It was demonstrated that the most active ligands behaved like agonists or partial agonists at postsynaptic 5-HT1A receptors.

Effect of the amide fragment on 5-HT1A receptor activity of some analogs of MP 3022.

A new set (3-11) of analogs of MP 3022 (1) containing the amide bond inserted into the intermediate chain linking the terminal heteroaromatic and 1-(2-methoxyphenyl)piperazine moieties were prepared and their 5-HT1A and 5-HT2A receptor affinities were determined. Only compounds with trimethylene chain between amide and arylpiperazine fragments (5a, 5b, 7a, 7b and 11) showed satisfactory affinity for 5-HT1A receptor (Ki = 42-87 nM) and high 5-HT2A/5-HT1A selectivity. The new 5-HT1A receptor ligands were investigated in vivo to determine their 5-HT1A agonistic or antagonistic properties. Compounds 7a and 7b with terminal indazole fragment as well as 11 with phenyl substituent behaved like weak 5-HT1A receptor antagonists. The structure-affinity relationship studies in this series of compounds revealed that the amide group along with the terminal aromatic fragments contributed to interaction with 5-HT1A receptor sites, whereas in vivo results indicated that introduction of the amide group into presented arylpiperazine structures was not a profitable modification for their 5-HT1A functional activity.

Some pharmacological properties of new analogs of MP 3022, the 5-HT1A receptor antagonist.

Two new analogs of full 5-HT1A receptor antagonist 4-[3-(1-benzotriazolyl)propyl]-1-(2-methoxyphenyl)piperazine (MP 3022; 1) containing di- (5) or tetramethylene- (6) spacer were synthesized. In the radioligand binding studies, compounds 5 and 6 showed high 5-HT1A (Ki = 14.7 nM and 11.8 nM, respectively) and low 5-HT2 receptor affinity (Ki = 2,696 nM and 389.2 nM, respectively). In behavioral studies both compounds behaved like postsynaptic 5-HT1A receptor antagonists as they reduced lower lip retraction and behavioral syndrome induced by 8-OH-DPAT (5-HT1A receptor agonist) in rats, but 6 was more effective in these tests. Derivative 5 did not affect body temperature in mice, whereas 6 decreased it. Furthermore, 5 did not change hypothermia induced by 8-OH-DPAT, and 6-induced lowering of body temperature in mice was not antagonized by (S)-WAY 100135 (5-HT1A antagonist), so in that model 5 and 6 did not behave as antagonist or agonist, respectively, at presynaptic 5-HT1A receptors. Compound 6 was studied in behavioral tests used to predict a potential anxiolytic (conflict drinking test in rats) and antidepressant (forced swimming test in rats) activity. Diazepam and imipramine were used as reference drugs. Compound 6 significantly increased the number of shocks accepted in water-deprived rats in conflict drinking test and shortened the immobility time in forced swimming test in rats. The above findings indicate that new 5-HT1A postsynaptic antagonist 6 behaves like anxiolytic and antidepressant, but mechanisms of these properties of 6 remain unknown.

A search for new 5-HT1A/5-HT2A receptor ligands. In vitro and in vivo studies of 1-[omega-(4-aryl-1-piperazinyl)alkyl]indolin-2(1H)-ones.

A series of 1-¿omega-(4-aryl-1-piperazinyl)alkyl]indolin-2(1H)-one derivatives 2-14 was synthesized in order to obtain ligands with a dual 5-HT1A/5-HT2A activity. The majority of those compounds (2-5, 7, 10-13) exhibited a high 5-HT1A (Ki = 2-44 nM) and/or 5-HT2A affinity (Ki = 51 and 39 for 5 and 7, respectively). Induction of lower lip retraction (LLR) and behavioral syndrome and inhibition of these effects evoked by 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) were used for determination the agonistic and antagonistic activity, respectively, at 5-HT1A receptors. The 5-HT2A antagonistic activity was assessed by the blocking effect on the head twitches induced by (+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) in mice. Two of the tested compounds, 1-¿3-[4-(3-chlorophenyl)-1-piperazinyl]propyl¿-6-fluoroindolin-2(1 H)-one (5) and 1-¿3-[4-(2-methoxyphenyl)-1-piperazinyl]propyl¿indolin-2(1H)-one (7), demonstrated a high 5-HT1A/5-HT2A affinity and an in vivo antagonistic activity towards both receptor subtypes.

Effect of linking bridge modifications on the 5-HT1A receptor activity of some 4-(omega-benzotriazol-1-yl)alkyl-1-(2-methoxy-phenyl)piperazines.

A new series of arylpiperazines with two (2a-4a) and four (2c-4c) methylene spacers was synthesized. Compounds 2a, 2c, 3c, 4a and 4c were found to be 5-HT1A ligands (Ki = 4-88 nM). The most promising compound, 2c, bound with the highest affinity (Ki = 4 nM) at 5-HT1A sites. The results of in vivo experiments showed that compounds 2a-4a were inactive, while 2c-4c revealed a distinct antagonistic activity towards postsynaptic 5-HT1A receptors. The pharmacological profile of the tested compounds was discussed in comparison with that of the three methylene analogs b, described earlier.

Anxiolytic- and antidepressant-like effects of an antagonist at glycineB receptors.

L-701,324 [7-chloro-4-hydroxy-3-(3-phenoxy)phenyl-2-(1H)-quinolone], a selective antagonist at glycineB receptors, was studied in behavioral tests used to predict a potential anxiolytic (conflict drinking test in rats, four-plate test in mice) and antidepressant (forced swimming test in rats and mice) activity. In the conflict drinking test in rats, L-701,324 (0.5 mg/kg, but not 0.25 and 1 mg/kg) increased the number of punished licks in a statistically significant manner. In the four-plate test in mice, L-701,324 (2 mg/kg, but no lower doses) significantly increased the number of punished crossings. In the forced swimming test in rats, L-701,324 (0.5 mg/kg) slightly, but statistically significantly, reduced the immobility time; the drug was inactive in doses of 0.25 and 1 mg/kg. In mice, L-701,324 administered only in the highest dose used (2 mg/kg) significantly shortened the immobility time. L-701,324 (given in doses higher then 2 mg/kg) induced motor impairment in animals. The above findings indicate that L-701,324 shows weak anxiolytic- and antidepressant-like activities in the animal models used.

1,4-Benzoxazin-3(4H)-one derivatives and related compounds as 5-HT1A and 5-HT2A receptor ligands; the effect of the terminal amide fragment on the 5-HT1A/5-HT2A affinity and functional activity.

A number of new 1-phenyl- (a), 1-(3-chlorophenyl)- (b) and 1-(2-methoxyphenyl)- (c) piperazine derivatives containing 1,4-benzoxazin-3(4H)-one (2-4), 2,4-benzoxazin-3-(4H)-one (5), 1,2-benzoxazolin-3-one (6) and 1,3-benzoxazolin-2,4-dione (7) were synthesized. Radioligand binding measurements showed that the majority of compounds had a distinct affinity for 5-HT1A (3a, 6a, 2-5b, 6c; Ki = 7.5-81 nM) and/or 5-HT2A (2b, 5-7a,b; Ki = 18-69 nM) receptors. Structure-Activity Relationship (SAR) studies revealed structural features which seem to favour the binding to either or both of these two receptor subtypes. For evaluation of the functional in vivo profile of the most potent 5-HT1A (5b, 6b) and/or 5-HT2A (5-7b) ligands, the following tests were used: the 8-OH-DPAT-induced lower lip retraction (LLR) and behavioral syndrome in rats--for 5-HT1A receptor antagonistic activity, and the (+/-)DOI-induced head twitches in mice and the (+/-)DOI-induced discriminative stimulus properties in rats--for 5-HT2A receptor antagonistic properties. The obtained results show that compounds 5b and 6c behave like potent 5-HT1A antagonists, whereas 5b, 6b and 7b demonstrate 5-HT2A receptor antagonistic properties. None of the in vivo tested compounds, given alone, mimicked 8-OH-DPAT activity in those tests. It seems that derivative 5b, which has an equipotent 5-HT1A and 5-HT2A affinity and antagonistic properties at both these receptors, is a promising potential psychotropic substance.